The invention relates to a foam element made from a foam and particles comprising at least one hydrophilic substance incorporated in the plastic, such as cellulose, superabsorbers, and the foam element containing the particles has a reversible capacity to absorb moisture.
These days, foams are used or employed in many areas of daily life. In many of these applications, the foams are in contact with the body, usually separated by only one or more textile intermediate layers. Most of these foams are made from synthetic polymers such as polyurethane (PU), polystyrene (PS), synthetic rubber, etc., which in principle do not have an adequate water absorption capacity. Particularly during longer periods of contact with the body or when undertaking strenuous exercise, an unpleasant physical climate develops due to the large amount of moisture that is not absorbed. For most applications, therefore, it is necessary for hydrophilic properties to be imparted to such foams.
This can be achieved in a number of ways. One option, as described in patent specification DE 199 30 526 A for example, is to render the foam structure of a polyurethane flexible foam hydrophilic. This is done by reacting at least one polyisocyanate with at least one compound containing at least two bonds which react with isocyanate in the presence of sulphonic acids containing one or more hydroxyl groups, and/or their salts and/or polyalkylene glycol ethers catalysed by monools. Such foams are used for domestic sponges or hygiene articles.
Another option is described in patent specification DE 101 16 757 A1, based on an open-pored hydrophilic aliphatic polymethane foam with an additional separate layer made from cellulose fibres with a hydrogel embedded in it, serving as a storage means.
Patent specification EP 0 793 681 B1 and the German translation of DE 695 10 953 T2 disclose a method of producing flexible foams, for which superabsorber polymers (SAPs), also known as hydrogels, are used. The SAPs which are used may be pre-mixed with the prepolymer, which makes the method very simple for the foam manufacturer. Such SAPs may be selected from SAPs grafted with starch or cellulose using acrylonitrile, acrylic acid or acrylamide as an unsaturated monomer for example. Such SAPs are sold by Höchst/Cassella under the name of SANWET IM7000.
Patent specification WO 96/31555 A2 describes a foam with a cellular structure and the foam also contains superabsorber polymers (SAPs). In this instance, the SAP may be made from a synthetic polymer or alternatively from cellulose. The foam used in this instance is intended to absorb moisture and fluids and retains them in the foam structure.
Patent specification WO 2007/135069 A1 discloses shoe soles with water-absorbing properties. In this instance, water-absorbing polymers are added prior to foaming the plastic. Such water-absorbing polymers are usually made by polymerising an aqueous monomer solution and then optionally crushing the hydrogel. The water-absorbing polymer and the dried hydrogel made from it is then preferably ground and screened once it has been produced, and the particle sizes of the screened, dried hydrogel is preferably smaller than 1000 μm and preferably bigger than 10 μm. In addition to the hydrogel, filler may also be added and mixed in before the foaming process, in which case the organic fillers which may be used include carbon black, melamine, rosin and cellulose fibres, polyamide, polyacrylonitrile, polyurethane or polyester fibres based on the principle of aromatic and/or aliphatic dicarboxylic acid esters and carbon fibres, for example. All of the substances are added to the reaction mixture separately from one another in order to produce the foam element.
In terms of their properties, foams known from the prior art are designed so that they are able to store and retain the moisture they absorb for a long period of time. The absorbed moisture and the absorbed water is not restored to the full initial state due to evaporation of the moisture to the ambient atmosphere until after a period of 24 hours, as explained in WO 2007/135069 A1.
This evaporation rate is much too slow for normal applications, such as in mattresses, shoe insoles or vehicle seats, for example, which are used for several hours a day and therefore have much less than 24 hours in order to evaporate the absorbed moisture. In this context, one might speak of an equilibrium moisture and the moisture value is that at which the foam is in equilibrium with the moisture contained in the ambient atmosphere. Accordingly, the underlying objective of this invention is to propose a foam element, which, in terms of its moisture management, has a high capacity to absorb moisture and then exhibits a high evaporation rate of the absorbed, stored moisture.
This objective is achieved in accordance with the invention. The advantage of the features according to the invention resides in the fact that even with a foam containing no added hydrophilic substance, a higher moisture absorption can be obtained for a pre-definable exposure to moisture, and this can be further improved by adding particles which absorb and rapidly evaporate moisture again. As a result, not only is it possible to absorb and store a high quantity of moisture over a given period during use, the moisture evaporates rapidly into the environment again after use. This means that a dried foam element is ready for use again after a relatively short period of time. A further advantage is that not all of the particles contained in the foam are completely surrounded by it, thereby offering greater possibilities for contact with the ambient conditions, both for the uptake of moisture and for evaporation of the moisture. This part-quantity of particles therefore results in a relatively rapid and high absorption capacity for the moisture or fluid to be absorbed, but the absorbed moisture or fluid is evaporated to the ambient atmosphere as rapidly as possible again from the state induced by use, thereby restoring the equilibrium moisture. This results in rapid removal of the moisture making renewed use possible within a short time.
The advantage of the features in an embodiment resides in the fact that in spite of the particles incorporated in the foam, a compression hardness suitable for the intended purpose can be obtained. This means that depending on the intended purpose of the foam element, compression hardness values can be pre-defined but the user can still be guaranteed optimum moisture management of the foam element as a whole. Due to the high value of the temporary storage of moisture or water which can be absorbed in the foam element during use, the user can be guaranteed to experience a pleasant and dry feeling during use. As a result, the body does not come into direct contact with the moisture.
The advantage gained as a result of the features in another embodiment resides in the fact that again depending on the intended purpose of the foam element, sufficient elasticity can still be achieved for different purposes in spite of the added particles constituting the hydrophilic substance, thereby imparting an associated support effect for the user of the foam element. Accordingly, it is possible to guarantee user comfort within predefined limits whilst simultaneously affording adequate moisture management.
The advantage gained as a result of the features in another embodiment resides in the fact that a high moisture absorption of the foam can be achieved which is higher than that of conventional foam. It is therefore not only possible to obtain a high capacity to absorb moisture, the latter is able to evaporate from the foam element at the end of use in a relatively short time, thereby rendering it fit for use again. This being the case, a dry foam element is quickly ready for use again.
The advantage gained as a result of the features in another embodiment resides in the fact that the foam proposed as an initial material already has a high absorption capacity without adding the hydrophilic substance, but this can easily by adapted to a range of different usage conditions by additionally incorporating the particles depending on the amount used as a proportion by weight. By varying the quantity of added particles, not only can the moisture management of the foam element be adjusted, the various associated strength values and elasticity can also be adjusted. The higher the proportion of particles is, the lower the elasticity, which can be compensated by increasing the weight by volume or density.
The advantage gained as a result of the features in another embodiment resides in the fact that due to the increase in the weight by volume or density in conjunction with the particles added with a view to obtaining good moisture management, sufficient elasticity values can also be obtained. As a result, not only is it possible to obtain a very high capacity to absorb water vapor and absorb moisture followed by a rapid rate of evaporation, the corresponding elasticity and the associated supporting effect for the user can be comfortably adjusted accordingly.
By adding cellulose to the foam structure in accordance with another embodiment, it is also possible to obtain a sufficient capacity to absorb moisture or fluid, and the absorbed moisture or fluid evaporates to the ambient atmosphere as rapidly as possible after use so that the equilibrium moisture is restored. As a result, whilst being comfortable to use, moisture absorbed by the foam element evaporates rapidly. This being the case, even after having absorbed a high amount of moisture, it can be used again even after a relatively short period of time and a dried foam element is quickly ready for use again.
Also of advantage is another embodiment, whereby depending on the resultant foam structure of the foam, the fiber length can be set so as to ensure optimum moisture transport, to obtain both rapid absorption and rapid evaporation after use.
An embodiment is also of advantage because it enables an even finer distribution of the cellulose particles in the foam structure to be achieved, as a result of which the foam element can be easily adapted to suit different applications.
Another embodiment enables the pouring capacity of the particles to be improved. The specific surface is increased due to the surface structure, which is irregular and not completely smooth, which contributes to an outstanding adsorption behavior of the cellulose particles.
Another embodiment offers the possibility of using such particles without clogging the fine orifices in the nozzle plate, even when using so-called CO2 foaming.
Also of advantage is another embodiment because a spherical shape is avoided as a result and an irregular surface without fibrous fraying and fibrils is obtained. A rod-shaped design is avoided and this is conducive to efficient distribution within the foam structure.
As a result of another embodiment, the absorption capacity and evaporation capacity of the foam element can be easily adjusted depending on the added proportion of cellulose, thereby enabling it to be adapted to different applications.
As a result of another embodiment, the cellulose can be added and displaced during the manufacturing process at the same time as at least one other additive, which means allowance has to be made for only a single additive when mixing it in a reaction component.
Also of advantage is another embodiment because it enables the use of particles which can be easily made from natural materials. This again enables the absorption capacity and evaporation of moisture of the foam element to be adapted to suit a range of different applications.
An embodiment is also of advantage because a natural material can be used but it is still possible to prevent unpleasant odors nevertheless.
As a result of another embodiment, the particles are additionally encased in a coating without impairing the capacity to absorb and evaporate moisture. This affords additional protection for the particles inside the foam element and enables deterioration of the particles to be delayed or even totally prevented, especially in the region of cut edges.
Based on another embodiment, mutual admixing of the particles in one of the base materials used to make the foam is prevented, thereby ensuring a uniform distribution of the particles inside the foam element as a whole during the foaming process. A virtually uniform distribution of particles through the entire cross-section of the foam element to be produced can be achieved as a result.
Also of advantage is another embodiment because the particles are disposed on the surface of cell walls and cell webs which means that there is a high concentration of particles for absorbing moisture and for moisture evaporation in these areas of foams with open pores. This enables the storage and evaporation behavior to be even further improved for example.
As a result of another embodiment, the coating applied to the foam element can be adapted to suit different applications because moisture can be absorbed by the surface of the foam element, which is already large in size, and evaporated through the particles contained in the coating.
As a result of another embodiment, adding a natural material has a positive effect on the user when he comes into direct or indirect contact with the foam element. The added material, which contains valuable substances, may also be used to provide a healing, soothing or protective effect.
An embodiment is of advantage because the foam element obtained can be used in a range of different applications.
Based on another embodiment, even better transport of the moisture inside the foam element is achieved.
Using the foam element for a range of different applications is also of advantage because it improves wearing comfort during use and the subsequent drying time is also significantly faster. This is of particular advantage in the case of different types of seats and mattresses, as well all those types of applications in which moisture is exuded by the body.
Embedding the particles inside the cell structure enables moisture to be absorbed by the particles disposed in the peripheral region of the cell walls and cell webs, which means that the space inside the cell walls and cell webs is also used for moisture management. This means that absorbed moisture can be directed from the particles disposed in the peripheral region into the interior of the foam structure. This further improves absorption capacity and subsequent evaporation of the moisture.